Reinforced concrete structure.



R B. TUFTS.

REINFORCED CONCRETE STRUCTURE.

APPLICATION FILED APILZB, 1914. y

Patented Feb; 27,1917.

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ROBERT B. TUFTS,'OF NORFOLK, VIRGINIA.

REINFORCED CONCRETE STRUCTURE.

Specification of Letters Patent.

Patented. Feb. 27, 1917.

Application led Apr128, 1914. Serial No. 834,995.

To all whom t may concern.'

Be it known that I, ROBERT B. TUFTs, of Norfolk, in the county of Norfolk and State of Virginia, have invented certain new and useful Improvements in Reinforced Concrete Structures; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

rThis invention relates to reinforced concrete floors, roofs, reservoir covers and the like,-the object of the invention being to attain to economy of material and cost of constructing the structure; to simplify and make more scientific the calculations of stresses, and to increase the safety of the structure, together with the attainment of various advantages as applied to certain specific conditions. f

Vith this object in view, the invention consists in composing each bay of a floor, roof or reservoir cover of a plurality of groined arch units arranged in two series of intersecting rows, each groined arch unit separated from its neighbor and partly supported by beams crossing each other, which in turn are monolithic with and supported by girders bordering all sides of and separating the bays.

The invention further consists in certain novel features of construction and combinations of parts as hereinafter set forth and pointed out in the claim.

In the accompanying drawings; Figure 1 is a plan view of a fragment of a floor, roof or reservoir cover embodying my improvements, said fragment comprising slightly more than one bay; Fig. 2 is a sectional view on the line -a of Fig. 1; Fig. 3 is an enlarged plan view of one of the groined arch units; Fig. l is a sectional view of said unit; Fig. 5 is a sectional View, on a larger scale than that of Fig. 2, illustrating the process of construction, with reinforcing bars in place for the girders and beams; Fig. 6 is a fragmentary sectional view similar to Fig. 5, but with the girders and beams complete and the false work removed; Fig. 7 is a sectional view similar to Fig. 2 but showing a modification in the width and depth of the beams and girders.

Preparatory to and in the early stages of the construction of a floor, roof or reservoir cover, I provide a suitable convex molding surfacektnt shown in the drawing)V and mold independent of and if desirable at a point distant from the structure, a suicient number of the groined arch units 1, generally rectangular in shape andwhich may be conceived to be two common arches intersecting each other,` the axes o f the two arches being substantially at right vangles to eachother. These units 1 may properly be called groined arches and may be more or less perfect in their molded. surfaces, but the important features are that they shall be approximate or perfect rectangles as the bays are approximately or perfectly rectangular in shape, and they shall further be shaped to act as arches by having their center portions of upper surface higher than the plane of the four sides. These units may have reinforcing bars or fabric embedded therein for increasing their strength, without altering the principles involved, but such reinforcement is not necessary to my invention and on the contrary the elimination of the necessity for reinforcement in the units is one of the desirable advantages attained by convexing these units.

These units l having been previously designed, dimensioned and molded in suiicient numbers andY beingV sufliciently hardened, they are positioned (see Fig. 5) on beam and girder molds 2 and 3, the sides of the beam or the beam and girder molds supporting on all four sides the unit 1. These sides of the beam and girder molds are less than the desired depth of beams and girders by an amount that will permit the edges of units 1 to be wholly below the tops of the beams and girders, so that the maximum contact will be obtained between beams and girders and the edges of the units l;

As shown by Figs. 5, 6 and 7 the units 1 willproject a slight amount into the spaces 4 and 5 which become'b'eams and girders when filled with concrete, so that after the beams and girders shall have been molded and become hard and the molds 2 and 3 removed, the units 1'not only have contact on all four sides with beams or beams and girders, but the latter afford gripping and supporting contact on all four sides.

It is clear that if the beams and girders are sufficiently stiH and strong both vertically and horizontally the peripheries of the groined arch units 1 will be held rigidly and these units being convexed upwardly in their center portion and otherwise properly shaped will act as arches in supporting lli) their' loads and will therefore be in compression throughout and will require no reinforcement. Since concrete is capable of withstanding great compressive strains, it requires no. argument to show that these units l may be of comparatively small thicknesses and therefore the groined arch units lend themselves to economical design as concerns material used.

rlhe beams and girders will be proportioned according to well known engineering theories to withstand bending and breaking tendencies arising from the loads to-be sustained, a due consideration of which will call for the beams being comparatively small with relation to the girders.

it will be observed that each bay is made with a plurality of the units l symmetrically arranged about the center of the bay, the dimensions of the units l, the beams G and 7 and the girders 8 and 9, being harmonized so that each will be of proper strength to carry the loads coming to' each.

lt is also clear that this design is best adapted to truly square bays but can be applied to bays of any shapes met with in construction., Then the bays are perfect squares, the units l are logically perfect squares and the dimensions of all beams are the same and of all girders are the same and the arrangement of units l and of beams and girders are symmetrical. Variations from perfect squares in the bays make corresponding variations in the units.

ln the drawings, nine groined arch units to each bay, are shown, and while this will often be the most suitable number, it is clear that more or less than this number may be employed. i

1Without ail'ecting the principles brought out, the beams and girders may be very wide and comparatively shallow as shown in Fig. 7 or they may be deep and narrow.

In order to attain to greatest economy in beam and girder design, all beams and girders will be reinforced by having bars near their under surfaces at and near midway between supports and these bars bent up and near the upper parts of beams at and near supports suiiicient lap being given the bars in girders over columns 11 (located at the corners of the bays) to insure them acting` as beams continuous over supports and the bars at the ends of beams likewise having suflicient embedment to insure the beams acting as rigidly fixed at their supports.

It is clear that superloads on the groi-ned arch units 1 by virtue of their arch action will exert horizontal thrusts on the beam or beams and girders performing the functions of abutments. It is also clear that for all beams and girders other than those Copies of this patent may be obtained `for bordering the eXtreme out-sides of the structure, the thrust from one arch will be counteracted by the equal and opposite thrust from its neighbor and therefore little or no attention need be taken of thesidewise thrust on the beams and girders except for the outside girders. The outside girders have unbalance thrusts, from the inside only, but these girders for other considerations will require to be comparatively wide and stiff, hence will require little or no additional sidewise stiffening to resist these thrusts. Y

As applied to Heers, the groined arches will give rise to irregular surfaces that will require iilling material to produce level surfaces, but for reservoir or roof constructions it is a common practice to place thereon two or three feet of earth lling in which case the irregular surface produced by the groined arches is not objectionable.

By studying the compressive stresses in the groined arches with due regard to the compressive strength of concrete Ait will be observed that theoretic requirements will generally call for surprisingly thin groincd arches and that it will be practically impossible to cause one of these groined arches to fail from a superposedload, providing the horizontal thrusts are resisted; all of which directs attention principally to strength of beams and girders, which latter can be logically assumed to be uniformly loaded and fixed at or continuous over supports, and therefore the analysis of stresses will be simpliiied and the conditions are favorable to economy of design.

Having fully described my invention what I claim as new and desire to secure by Letters-Patent, is

A concrete structure comprising a plurality of concrete girders arranged in rectangular formation, transverse concrete beams dividing the space bounded by said girders into smaller spaces, said girders and beams forming a monolithic structure, and comparatively thin precast groined arch panel units, each having less thickness than tiat of the girders and beams, said groined arch panel units closing said smaller spaces and having their edge portions embedded in the walls of the monolithic structure intermediate the upper and lower faces of the same, and supported by said monolithic structure.

ln testimony whereof, I have signed this specification in the presence of two subscribing witnesses.

ROBERT B. TUFTS.

Witnesses:

JNO. H. LOWE, J. H. VVnAvnn.

ve cents each, 'by addressing the Gommissonei' 0f latentsJ Washington, D. C.

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